1. Field of the Invention
The present invention relates generally to demodulators in mobile communication systems and, in particular, to a demodulator for despreading data transmitted in a multicode CDMA system that allocates multiple codes to each user.
2. Description of the Related Art
In transmitting data, a Code Division Multiple Access (CDMA) system allocates a single code to each user. A time tracker used in a common CDMA system is structured to demodulate data by tracking the single code. However, to meet an increasing demand for fast data transmission in radio mobile communication, a technology has been proposed which allocates multiple codes to each user in order to transmit an increased amount of data per unit time. Nonetheless, the conventional time tracker cannot time-track the input data spread by the multiple codes to extract the data. Further, the conventional time tracker cannot demodulate the data by the codes.
It is an object of the present invention to provide a demodulator for despreading data in a multicode Code Division Multiple Access (CDMA) system in order to demodulate the data.
To achieve the above object, there is provided a data demodulator for a multicode CDMA system, the system transmitting data by allocating multiple codes to each user. The data demodulator includes a code generating part that generates a local code and local orthogonal codes for respectively despreading input channels signals and orthogonally despreading the despread channel signals. A time error estimator generates time error information for the despread channel signals and outputs the time error information to the code generating part. A symbol processing part includes N symbol processing units, where N is the number of codes allocated to each user. The N symbol processing units demodulate symbols despread by the local orthogonal codes into original symbols. A symbol deskewer classifies the demodulated symbols by the respective codes and writes the classified symbols in sequence into a two-dimensional memory.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.